RSpecMatchAsserter supports rspec-3.0.0.rc

Some notes:

1. This supports all `rspec-3.0.0.rc` versions. The conditional in `lib/surrogate/rspec/with_filter.rb` will need to be updated when `rspec-3.0.0` officially comes out.
2. I've included a `Gemfile` specifically for `rspec-3.0.0.rc` versions.
3. I probably messed up, but I gave it up a minor bump. It should not affect existing users.
4. The updates to `spec/unit/argument_errorizer_spec.rb` will only work for `rspec-3.0.0.rc` or newer.